Externalizing behavior problems in preschool children may represent part of normal developmental behaviors; however, if they persist, they can lead to serious psychological and social difficulties in the future. Deficits in emotional self-regulation are key factors in the development of such problems. The present study aimed to investigate the effectiveness of a unified program based on transdiagnostic treatment, focusing on teaching cognitive and emotional self-regulation skills, in reducing externalizing behavior problems among preschool children with behavioral disorders. An experimental single-subject design was employed and conducted in a preschool center in Shahrekord. The statistical population consisted of all preschool children aged 5 to 6 years with behavioral disorders who were enrolled in preschools in Shahrekord during the 2024-2025 academic year. Sampling was performed through purposive sampling based on specific criteria. The research instruments included the Achenbach Child Behavior Checklist (1991) and the Shields and Cicchetti Emotion Regulation Checklist (1997), completed by mothers during the three phases of baseline, intervention, and follow-up. The intervention program was conducted in ten sessions and consisted of two separate sections for children and parents. The parent sessions lasted 45 to 60 minutes, and the child sessions lasted 20 to 30 minutes. The findings indicated that after implementing this program, the children’s behavioral symptoms showed considerable improvement across multiple dimensions, particularly in the externalizing behavior and emotional regulation subscales. The results demonstrated the effectiveness of the unified cognitive and emotional self-regulation program in reducing externalizing behavior problems and improving emotion regulation skills in preschool children.
